When to Write a User-level Device Driver

• If your user does not need to use EISA device interrupts or DMA operations.

  Tip: On many EISA boards that generate interrupts or use DMA operations, these features can be disabled so that simple, user-level drivers can be used.

• It is more convenient to write a user-level EISA-bus device driver to determine whether a device is responding to the correct address or simple register tests.

  Tip: This can be very useful for prototyping: you can quickly integrate boards into a system with the interrupts turned off, then later write a kernel-level driver that uses interrupts or DMA operations for better performance.

• You can use a user-level device driver in real applications that require low-overhead access to on-board device registers or memory.